FMGE – Biology: Reproduction
(Comprehensive, concise, and exam‑ready notes)
1. Simple Explanation
Reproduction is the biological process by which organisms produce new individuals.
- Asexual reproduction: One parent → identical clone (binary fission, budding, vegetative propagation).
- Sexual reproduction: Two parents → genetically diverse offspring (gametes fuse → zygote).
In humans, reproduction is sexual, involving gametogenesis, hormonal regulation, fertilization, embryogenesis, and lactation.
2. Key Points
| Aspect | Human Reproduction |
|---|---|
| Gametes | Sperm (male, 1n=23) + Egg (female, 1n=23) |
| Spermatogenesis | 1 primary spermatocyte → 4 spermatids → 4 sperm (continuous, ~8 weeks) |
| Oogenesis | 1 primary oocyte → 1 mature ovum + polar bodies (stages arrested at prophase I) |
| Hormonal Control | GnRH → LH & FSH → ovarian & testicular functions |
| Menstrual Cycle | Follicular phase (days 1‑14), ovulation (day 14), luteal phase (days 15‑28) |
| Fertilization | Capacitation → acrosome reaction → penetration of zona pellucida → fusion of pronuclei |
| Embryonic Development | Pre‑implantation (zygote → morula → blastocyst) → Implantation (days 6‑10) |
| Placental Formation | Chorionic villi → maternal blood supply |
| Lactation | Prolactin & oxytocin → milk synthesis & let‑down |
| Key Terms | Gametogenesis, Fertilization, Zygote, Cleavage, Morula, Blastocyst, Implantation, Placenta, Lactation |
3. Worked Example
Question
A male undergoes a testicular biopsy that shows 2 × 10⁶ primary spermatocytes per gram of testis.
a. How many mature sperm cells are produced per gram of testis?
b. If each sperm has a 50 % chance of fertilizing an ovum, what is the expected number of successful fertilizations per gram?
Solution
| Step | Calculation | Result |
|---|---|---|
| a. Spermatogenesis | 1 primary spermatocyte → 4 spermatids → 4 sperm | 2 × 10⁶ × 4 = 8 × 10⁶ sperm per gram |
| b. Fertilization probability | 8 × 10⁶ sperm × 0.5 = 4 × 10⁶ fertilizations per gram |
Answer:
- (a) 8 × 10⁶ mature sperm per gram.
- (b) 4 × 10⁶ expected fertilizations per gram.
4. Quick Revision Summary
| Topic | Key Take‑away |
|---|---|
| Spermatogenesis | 4 sperm per primary spermatocyte; continuous; 8 weeks. |
| Oogenesis | 1 ovum per cycle; polar bodies discarded; 2 nd meiotic division completes at fertilization. |
| Hormonal Cycle | GnRH → FSH (follicular growth) + LH (ovulation); estrogen → cervical mucus; progesterone → endometrial thickening. |
| Fertilization | Capacitation → acrosome reaction → zona pellucida penetration → pronuclei fusion. |
| Embryo Stages | Zygote → 2‑cell → 4‑cell → morula → blastocyst (inner cell mass + trophoblast). |
| Implantation | Blastocyst adheres to endometrium (days 6‑10); trophoblast forms placenta. |
| Placenta | Chorionic villi → maternal blood → nutrient & waste exchange. |
| Lactation | Prolactin → milk production; oxytocin → let‑down reflex. |
Quick Flashcard‑Style MCQs
-
Which hormone peaks just before ovulation?
A. FSH B. LH C. Estrogen D. Progesterone
Answer: B. LH -
What is the first cellular event of fertilization?
A. Acrosome reaction B. Pronuclei fusion C. Sperm capacitation D. Zygote formation
Answer: A. Acrosome reaction -
How many polar bodies result from a human oocyte?
A. 1 B. 2 C. 3 D. 4
Answer: B. 2 -
Which structure gives rise to the chorionic villi?
A. Inner cell mass B. Trophoblast C. Endoderm D. Mesoderm
Answer: B. Trophoblast
Use these notes to reinforce concepts, practice calculations, and master key terminology for the FMGE Biology exam. Happy studying!